double...er...deutsch

Having a bit of trouble with my German coursework, wondered if anyone can help???? Trying to write a piece about a young man from one of the bands I'm in and despite having three fairly large dictionaries, I have aboslutely no idea how to say the following: cornet, trumpet, brass band, pickled onions, mouthpiece brush and public school (as in English public school). Could any kind German speaking tmpers help me out??? Thank you

(entschuldiging, aber ich kan nur Deutsch sprechen wan ich eine heisse kartoffel in mein offnung(?) habe <- I only learned a little bit of German from listening to other people speaking it + there are some similarities with Dutch of course)